Vacuum has traditionally been a primary motive force for many control functions within motor vehicles, particularly automobiles. Although electro-mechanical actuators have displaced vacuum motors for certain functions, vacuum remains the preferred method of modulating such automotive operating parameters as ignition timing, emissions control, throttle (cruise control) position and the like.
Ever increasing complexity required to conform with governmental regulations and added vehicle features has necessitated the addition of intelligence to certain control functions. Prior Art processing of vacuum signals however, typically has been limited to dedicated, signal function devices, such as a vacuum motor for modulating and exhaust gas recirculation (EGR) valve. Where intelligence or complex processing was required, discrete separate components were generally coupled or cascaded to achieve the required processing capability.
The competitive nature of the automobile industry however, typically makes the coupling of two or more established components to perform a single new function, cost prohibitive. For this reason, existing vacuum devices often prove unacceptable for new applications, especially where complex processing is required. The application of electronic processors has ameliorated the situation somewhat but has introduced additional shortcomings. Electromechanical actuators are heavy and expensive, and are often unsuitable for low-force functions. Additionally, electronic processors require pneumatic and/or mechanical-electrical transducers which add more expense. Also, the use of custom design electronics and electro-mechanical devices can be cost ineffective in applications where design changes are frequently made.